Move plugins out of src/plugins/ into plugins/ (upper directory).
This movement makes rebuild of panel itself simpler when you change something.
This also makes sense because plugins are somehow distinct from panel.

Reuse PanelToplevel window as actual panel class.
This way we can:
1) spare destroying function, just use gtk_widget_destroy();
2) simplify access Plugin->Panel to gtk_widget_get_toplevel();
3) simplify access toplevel window of Panel to GTK_WINDOW(p).
Old Panel is priv mamber of new LXPanel class. No extra memory consumed
because we can remove topgwin member from Panel structure later.

Use gtk_widget_destroy() instead of gtk_container_remove() if possible.2014-08-13T19:22:04ZAndriy Grytsenkoandrej@rep.kiev.uaAndriy Grytsenkoandrej@rep.kiev.ua2014-08-13T19:22:04Zhttps://git.lxde.org/gitweb/?p=lxde/lxpanel.git;a=commitdiff;h=5b3976380dd7f9efa32f03417214befbeccaf838

Use gtk_widget_destroy() instead of gtk_container_remove() if possible.
In most of cases the widget is not referenced and is lost anyway
therefore there is no reason to use gtk_container_remove() for it.

Replace all the deprecated APIs with used in GTK 2.24.x.2014-07-25T18:33:51ZAndriy Grytsenkoandrej@rep.kiev.uaAndriy Grytsenkoandrej@rep.kiev.ua2014-07-25T18:33:51Zhttps://git.lxde.org/gitweb/?p=lxde/lxpanel.git;a=commitdiff;h=09fa171bf8e302da915fbce7958460e78eef714c

Replace all the deprecated APIs with used in GTK 2.24.x.
Also raise min GTK+ version to 1.18 - that is required by LibFM anyway.

Heavy rewriting in many areas2009-07-08T19:43:43Zmartyj19martyj19@comcast.netmartyj19martyj19@comcast.net2009-07-08T19:43:43Zhttps://git.lxde.org/gitweb/?p=lxde/lxpanel.git;a=commitdiff;h=2918994ead02888b43061a450648404fa02868ca

Heavy rewriting in many areas
Reference release notes in mailing list lxde-list and on forum
Bump release ID to 0.4.990
New wincmd icon from http://www.oxygen-icons.org/ (licensed under LGPL).
- Given proper attribution in AUTHORS
Updated LINGUAS, oversight on one language